In recent years, hybrid vehicles are the focus of public attention due to the growing societal need for fuel efficient vehicles. Hybrid vehicles utilize an internal combustion engine and a motor-generator to provide both fuel-efficient and low-emission transportation.
Generally, an electrically-heated catalyst (designated as an “EHC” hereinafter) may be used to purify the exhaust gas of the internal combustion engine, in which the EHC may be heated by electric power from the battery. In some hybrid vehicles, the EHC may be heated by electric power from the battery when the internal combustion engine has not yet been started (e.g., during an EV travel period in which the hybrid vehicle may be propelled solely by the motor-generator). The EHC may be preheated to an activating temperature prior to the starting up of the internal combustion engine. As a result, upon start-up, the purification rate of the exhaust gas from the internal combustion engine may be improved.
However, in the above-described technique, the electric power required for the propulsion of the hybrid vehicle while heating the EHC via electric power (during the “e-power” heating time of the catalyst, hereinafter) is not taken into account. That is, until the completion of the warm-up of the EHC, the internal combustion engine will not be started. Therefore, during the e-power heating of the EHC, a shortage of the electric power required for the travel of the hybrid vehicle may be experienced.
Therefore, as disclosed in a patent document 1 (i.e., Japanese Patent Laid-Open No. 2011-105133), in case A, if, during the e-power heating time of the EHC while the internal combustion engine is stopped (e.g., while the vehicle is traveling solely on electric power such as during an EV travel period), the driving power Pr required for the travel of the vehicle is equal to or less than the difference between a battery output restriction Wout (i.e., a threshold/maximum amount of electric power supplied by the battery) and a basic e-power supply Phtmp (i.e., a basic amount of electric power supply for the EHC), in other words (Wout−Phtmp), the electric power supply for the EHC is controlled and set to a value equal to the basic e-power supply Phtmp. In case B, if, during the same e-power heating time of the EHC during the EV travel period, the required driving power Pr is (a) greater than the difference between the battery output restriction Wout and the basic e-power supply Phtmp and (b) equal to or smaller than the battery output restriction Wout, the electric power supply for the EHC is controlled and set to a value equal to the difference between the battery output restriction Wout and the required driving power Pr (i.e., Wout−Pr).
However, in the technique disclosed in the patent document 1, while the e-power heating of the EHC is controlled, the electric power consumption due to the starting up of the internal combustion engine and/or the electric power consumption due to supplemental devices such as an air-conditioner, is not considered. Therefore, in the technique of patent document 1, such problems may occur during the e-power heating of the EHC. That is, (i) when a start request for the starting up of the internal combustion engine is generated during the e-power heating of the EHC, the internal combustion engine may fail to start due to a lack of electric power required to start the engine. Or, (ii) even when the starting up of the internal combustion engine is normally performed, the drivability of the vehicle may be deteriorated due to a decreased amount of the electric power available for the travel of the vehicle, caused by the large consumption of electric power used for the starting up of the internal combustion engine. Or, (iii) a restriction value (e.g., the maximum value) of the electric power output from the battery may be exceeded, thereby deteriorating the battery.